Field of the Invention
The present invention relates to a rotary type gas compressor having a multi-stage compression function, and, more particularly, to an improvement in the back pressure application to a vane for sectioning a cylinder of a low stage compression element into a suction chamber and a compression chamber and an improvement in the oil supply.
Recently, in the art of refrigerators a serviceable refrigerant compressor suitable for performing a high compression ratio operation has been studied in order to obtain a satisfactory low temperature heat source.
In particular, a variety of multi-stage rotary type compressors have been proposed in order to improve the compression efficiency by reducing the quantity of gas leaked during the compression operation by reducing the pressure difference between the compression chamber and the suction chamber.
Specifically, a rolling piston type two stage rotary compressor and the system of a two stage rotary compression refrigerating cycle constituted by connecting the rolling piston type two stage rotary compressor arranged as shown in FIGS. 11 to 13 have been proposed.
Referring to FIGS. 11 to 13, a driving electric motor 1005 is disposed in the upper portion of a closed container 1003. Furthermore, a compression mechanism comprising two stages (the upper stage comprises a low pressure compression mechanism 1007 and the lower stage comprises a high pressure compression mechanism 1009) and connected to a rotational shaft 1005c of a driving electric motor 1005 is disposed in the lower portion of the closed container 1003. In addition, an oil reservoir is disposed in the bottom portion. Furthermore, the back side of a vane 1007c (1009c) for sectioning each cylinder of the low pressure compression mechanism 1007 and the high pressure compression mechanism 1009 into a suction chamber and a compression chamber is connected to the space in the closed container 1003. As a result, a back pressure applied to the vane 1007c (1009c) is composed of the reaction of a spring device and the pressure in the closed container 1003.
A refrigerant gas discharged from the low pressure compression mechanism 1007 is introduced into an external gas-liquid separator 1017 via a discharge pipe 1007e' before it is again introduced into the closed container 1003 via a connecting pipe 1009d'. As a result, the driving electric motor 1005 is cooled off.
The discharged refrigerant gas again introduced into the closed container 1003 absorbs lubricating oil present in the bottom portion of the closed container 1003 when it passes through a suction pipe 1009d having an oil suction pipe 1023. Then, the discharged refrigerant gas which has absorbed lubricating oil is introduced into the high pressure compression mechanism 1009 so that lubricating oil is used to cool the sliding surface and seal a gap formed in the compression chambers.
The discharged refrigerant gas again compressed by the high pressure compression mechanism 1009 is introduced into an external condenser 1013 via a discharge pipe 1009e before it sequentially passes through a first expansion valve 1015, a gas-liquid separator 1017, a second expansion valve 1019 and an evaporator 1021. The discharged refrigerant gas is then again fed back to the low pressure compression mechanism 1007 via a suction pipe 1007d.
The two stage compression refrigerating cycle is constituted by the above-described refrigerating circulation so that the internal space of the closed container 1003 is maintained at an intermediate level between the pressure of the condensed refrigerant and the evaporation pressure (refer to Japanese Patent Unexamined Publication No. 50-72205).
In the structure constituted as shown in FIGS. 11 to 13, the force to be applied to the back side of the vane 1007c of the low pressure compression mechanism 1007 depends upon the resultant force of the pressure force of lubricating oil on which the intermediate pressure (equivalent to the pressure discharged from the low pressure compression mechanism 1007) in the closed container 1003 acts and the reaction force of the spring device. However, the body force to be applied to the back side of the vane 1009c of the high pressure compression mechanism 1009 depends upon only the reaction force of the spring device.
Therefore, even if the pressure in the cylinder of the high pressure compression mechanism 1009 is raised, the vane 1009c must be able to section the interior of the cylinder into the suction chamber and the compression chamber while preventing instantaneous jumping and retraction. In order to achieve this, the tip end of the vane 1009c must be always brought into contact with the surface of a rotary ring 1009b while overcoming the compression pressure. Therefore, there arises a necessity of using a great spring force in order to counter the compression pressure in a case where the pressure in the cylinder is raised. Therefore, in a case where the condensation pressure is produced in two stage compression in a state of stationary pressure, the tip end of the vane 1009c is strongly pressed against the rotary ring 1009b because the pressure in the cylinder of the high pressure compression mechanism 1009 is not sufficiently high. As a result, the tip end of the vane 1009c will be excessively worn and the frictional loss increases, causing a problem to arise in that the durability is deteriorated and the input loss increases.
In Japanese Patent Unexamined Publication No. 50-72205, a structure has been described as a conventional structure in which the closed container 1003 is filled with a high pressure refrigerant gas the pressure level of which is equivalent to the condensation pressure by introducing the gas discharged from the high pressure compression mechanism 1009 into the closed container 1003 in addition to the structure in which the inside portion of the closed container 1003 is made to be at the intermediate pressure as shown in FIGS. 11 to 13.
However, contrarily to the case shown in FIGS. 11 to 13, the above-described structure is arranged in such a manner that the back side of the vane 1007c of the low pressure compression mechanism 1007 is urged by a resultant force composed of the pressure force of lubricating oil on which the high pressure refrigerant gas acts and the reaction force of the spring device. As a result, the tip end of the vane 1007c is always pressed against to the rotor ring 1007b with an excessively large urging force. Therefore, similarly to the structure shown in FIGS. 11 to 13, there arises a problem in that the durability is deteriorated and the input loss increases due to the excessive wear of the tip end of the vane 1007c and the increase in the frictional loss.
Furthermore, since the quantity of introduction of lubricating oil present on the back side of the vane 1007c into the cylinder via the gap on the sliding surface increases, there arises a problem in that the input is further undesirably increased due to the oil contraction. Therefore, a two stage rotary type refrigerant compressor exhibiting durability and the compression efficiency equivalent to those of a single stage compression rotary type compressor for a low compression ratio has not been realized as yet.